1. Field of the Invention
The present invention relates to an automatic quality control system, and more particularly to an automatic quality control system useful for work processed under quality control according to estimated characteristics and trends of processing machines based on measured values of processed works. The invention relates more particularly to an automatic quality control system capable of operating control elements to maintain quality standards thereby permitting a reduction in the cost and labor of control processing.
2. Description of the Prior Art
All or most quality control procedures such as measurement of processed work, data processing, estimation of characteristics of processing machines, and inspection of quality deviation have been dependent upon human skill. In such a system, control limits computed on the basis of measured values collected from work portions are used without modification over a certain period until defective quality is encountered. In other words, the prior art has failed to take into consideration the variation in the characteristic and trends of processing machines as they are operated. As a result, the processed work does not always meet predetermined quality standards with the result that productivity is lowered. One solution to this problem has been to narrow the range of control limits. This, however, has necessitated frequent positional adjustment or even change of tools with the result that the processing cost increases. In the prior art, the range of adjustment of tool positions is fixed and it is therefore difficult to adequately compensate for the processing machine characteristics which vary during operation. If the available adjustments are inadequate, the occurrence of defective quality becomes frequent, the tool position must be adjusted often and down time increases causing processing efficiency to be lowered. The need for extra labor in a prior art automated process line arises in most cases from the lack of an efficient feedback system associated with a group of machine tools.